It is a known procedure, and prescribed by law in most countries, to monitor electric circuits for the occurrence of so-called residual currents or ground residual currents. If such a residual current is ascertained which has exceeded a given value, the electric circuit in question is switched off by a residual-current circuit breaker. The specific value at which an electric circuit is switched off is, for example, a mere 30 mA, the limit for ventricular fibrillation in humans.
A drawback here is that, aside from the actual source of the fault, all of the other pieces of electrical equipment are also switched off. In the currently usual situation, it is not possible to continue to operate an electrical system with such a low-resistance ground connection. The residual-current circuit breaker in question is immediately switched off as soon as an attempt is made to once again start up the affected electric circuit or the affected electrical system. The system can only be restarted once the fault has been remedied.